JPH0220802B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to steam turbines, and more particularly to a partition plate containing steam guiding and accelerating vanes for impinging the rotor blades of a steam turbine.

Traditionally, steam turbines use a nozzle formed by a plurality of fixed vanes arranged in a steam passage, and such a nozzle smoothly redirects and accelerates the incoming steam in a desired direction, and flows into the turbine. It is aerodynamically designed to impact the moving blades. Accuracy within the steam path is important for turbine rotor blades. This means that steam must be guided with precision using precisely shaped and stably supported partition vanes to avoid power-wasting turbulence and undesigned flow characteristics.

Steam turbine partitions have traditionally been formed by inserting the ends of the blades into cutouts in semicircular metal bands known as spacers. After the ends of such vanes are tack welded to the spacer, the outer and inner semicircular rings are permanently welded to the spacer and vane. In order to achieve a satisfactory bond between the vanes and the ring, a very deep weld must be made between the ring and the spacer so that the weld penetrates deep enough into the interface between the two to provide a contact bond to the vanes as well. It is necessary to do so.

As described in U.S. Pat. No. 4,288,677,
As the depth of penetration increases, the number of weld defects also increases. Such welding defects include, for example, cracks,
Examples include slag entrainment and incomplete penetration, which can lead to damage or instability of the nozzle blades. Additionally, such deep welds tend to cause distortion of the steam path resulting in a deviation from the designed aerodynamics, thereby reducing the overall efficiency of the device.

The thickness of the spacer has typically been relatively small (eg, less than 1/4 inch). The reason for this is that there is a limit to what can be processed using conventional punching techniques. This small thickness made the spacer more useful as a positioning member prior to welding to the inner and outer rings than as a structural member capable of supporting the vanes in its own right.

Another source of distortion was the assembly of the spacer and vanes into a semicircular subassembly. Distortion from heating, shrinkage during welding, material stress relief treatments, and tempering tended to cause distortion of the subassembly both before and after joining with the inner and outer rings. It is believed that such distortion is due, at least in part, to stress variations in the semicircular subassembly causing distortion of the semicircle.

Conventional manufacturing techniques have used flat radial mating surfaces to join partition subassemblies. As a result, it has typically been necessary to cut the nozzle vanes at each end of each semicircular subassembly due to the tangential overlap of the nozzle vanes. In this case, relatively flexible vane segments would be present in the steam path, which could cause distortion and vibration, reducing the aerodynamic efficiency of the steam flow.

OBJECTS OF THE INVENTION One of the objects of the invention is to provide a partition plate for a steam turbine that eliminates the disadvantages of the prior art.

It is also an object of the invention to provide a partition plate for a steam turbine having an improved aerodynamic nozzle.

Furthermore, as a result of the nozzle vanes being structurally fixed to the strap and the strap having a 360 degree annular structure,
It is also an object of the invention to provide a partition plate for a steam turbine in which distortions due to assembly deviations, thermal and shrinkage stresses are reduced and tighter tolerances can be held. be.

Furthermore, it is an object of the invention to provide a partition plate for a steam turbine in which the separation between 180 degree sectors of the steam passage is along the cutting plane between adjacent blades.

Furthermore, the present invention provides a partition plate for a steam turbine in which the straps located at both ends of the blades are cut along the curved cutting plane between adjacent blades, and the mating surfaces of the inner and outer rings are flat. It is also an object of the present invention to provide.

According to one aspect of the invention, a semicircular inner strap;
A steam passage is formed by a semicircular outer band that is arranged concentrically with the inner band, and a plurality of blades that are arranged between the inner band and the outer band. The inner end and the outer end fit into slots provided in the inner strap and the outer strap,
The inner and outer ends of the vanes are secured to the inner strap and the outer strap by structural welds, and the inner strap includes welds located at the upstream and downstream interfaces on the inner surface of the inner strap. A semicircular inner ring is thus fixed, a semicircular outer ring is fixed to the outer surface of the outer strap by welds located at the upstream and downstream interfaces, and the inner strap, the 180 for a turbine, wherein the outer strap and the structural welds are effective to support the blade without requiring welds between the blade and the inner ring and the outer ring;
A half-partition plate is provided.

According to another aspect of the invention, (a) forming a 360 degree inner band, (b) forming a 360 degree outer band, and (c) accommodating the inner and outer ends of the vane. a plurality of slots are provided in the inner strap and the outer strap, (d) the inner strap and the outer strap are held coaxially, and (e) a plurality of the vanes are inserted into the slots. (f) tack welding said inner and outer ends of said vane to said inner and outer ferrules; and (g) a weld effective to minimize distortion of the steam passage formed. structurally welding the inner and outer ends of the vane to the inner and outer straps according to the procedure; (h) stress relieving and tempering the steam passage; and (i) Approximately along the first and second cut planes located midway between adjacent blades.
A method of forming a steam passageway in a steam turbine partition plate is provided, characterized in that it comprises the steps of cutting the inner band and the outer band at two points separated by 180 degrees.

According to yet another aspect of the invention, (a) forming a 360 degree inner band; (b) forming a 360 degree outer band;
(c) providing a plurality of slots in the inner strap and the outer strap for accommodating the inner and outer ends of the vanes;
(d) holding the inner strap and the outer strap coaxially; (e) inserting a plurality of the vanes into the slot; (f)
(g) tack welding the inner and outer ends of the vane to the inner and outer straps, and the inner and outer ends of the vanes are structurally welded to the inner and outer straps; (h) the steam passageway is stress-relieved and tempered; Approximately 180 degrees along the first and second cutting planes located at
(j) cutting the inner strap and the outer strap at two points separated by an angle of 180 degrees to create first and second steam passage sections; Forms a half-ring inside the degree,
(k) securing said inner half-ring to said inner ferrule of each said steam passage section with welds located at the upstream and downstream interfaces; and (l) having generally flat mating surfaces at each end. forming a pair of 180 degree outer half-rings, and then (m) securing said outer half-rings to said outer strap of each said steam passage section using welds located at the upstream and downstream interfaces; A method for manufacturing a turbine partition plate is provided, which is characterized by comprising various steps.

These and other objects, features, and advantages of the present invention will become apparent upon reading the following description in conjunction with the accompanying drawings. In addition, the same components are indicated by the same reference numerals in the drawings.

DESCRIPTION OF THE EMBODIMENTS First, looking at FIG.
A cross-sectional view of an axial steam turbine 10 including 4 is shown. A plurality of turbine rotor blades 16 are fixed to shaft 14 in a conventional manner so as to rotate therewith. The inlet partition plate 18 includes annularly arranged vanes 20 so that the steam introduced from the steam chamber 22 is guided and accelerated to impinge on the first row of turbine rotor blades 24 .

A subsequent partition plate 26 separates each pair of turbine rotor blade rows 16.
It serves to guide and accelerate the steam entering from the upstream side again, and to impact the downstream turbine rotor blade row at an optimal angle and flow velocity.

Each partition plate 26 includes a vane 20 between an outer spacer 28 and an inner spacer 30.
An outer ring 32 is secured to the outer spacer 28 and engages the passenger compartment 12 in a conventional manner. An inner ring 34 is fixed to the inner spacer 30 and is suspended at a distance from the shaft 14. As usual, rotating shaft 14
A shaft sealing means (not shown) is provided in a sealing portion 36 located at the inner end of the inner ring 34 to rotate the shaft 14 relative to the partition plate 26 while preventing axial steam leakage along the shaft. You can also do that.

Turning now to FIG. 2, there is shown an axial cross-sectional view of a partition plate made in accordance with the prior art. First, the vanes 20 are tack welded to the outer spacer 28 and inner spacer 30. Next, the feather 20
are seal welded to the outer and inner spacers at locations 40 and 42, respectively. As a result,
The outer spacer 28, the inner spacer 30, and the vane 20 are held in a semicircular assembly, which is a welded portion 44, 4 with a large penetration depth.
6, 48 and 50 are welded to the semicircular outer ring 32 and inner ring 34. In addition,
Each of the welds 44-50 penetrates deep into the spacer-ring interface and contacts the distal ends of the vanes 20, thereby connecting the vanes 20 to the rings 32 and 3.
It should be noted that it is firmly fixed to 4. That is, the spacers 28 and 30 are primarily used for positioning the blades 20, and only after being welded to the outer ring 32 and the inner ring 34, which form the structural support, can the blades 20 be positioned.
is firmly fixed.

Turning now to FIG. 3, a cross-sectional view of a partition plate according to the present invention is shown. In this case, the outer strap 52
and inner strap 54 have slots 56 and 5, respectively.
8, including the distal end 6 of the vane 20.
0 and 62 are inserted. Ends 60 and 6
2 are firmly welded to the outer strap 52 and the inner strap 54, respectively, as shown at 64 and 66, prior to assembly with the outer ring 32 and inner ring 34. As will be described later, the welds at 64 and 66 are performed when the bands 52 and 54
It is carried out while having a complete annular structure melt of 360 degrees. The thickness and strength of straps 52 and 54 are sufficient to serve as complete structural support for vane 20 without the need for direct welding to outer ring 32 and inner ring 34. As a result, the outer strap 52 has the smallest weld 68
and 70 to the outer ring 32. That is, those welds only need to firmly fix the upstream and downstream ends of the band 52 to the ring 32, and the welds only need to firmly fix the upstream and downstream ends of the band 52 to the ring 32.
There is no need to touch 0. Similarly, the upstream and downstream ends of strap 54 are secured to inner ring 34 by minimal welds 72 and 74, which welds connect distal ends 62 of vanes 20.
There is no need to come into contact with it.

In some cases, the outer strap 52 may be flared as shown to allow steam expansion.

Turning now to FIG. 4, a preassembly consisting of inner strap 54, outer strap 52 and vane 20 is shown. Inner strap 54 and outer strap 52 are formed by bending the strips to form a ring, suitably welding the ends of the strips together, and then stress relieving and tempering the rings in a conventional manner. By doing so, it is sufficient to obtain a 360 degree annular structure as shown in the figure. Slot 56 in outer strap 52 and slot 58 in inner strap 54
Although slots 56 and 58 may be formed by any suitable method, such as electrical discharge machining, in accordance with a preferred embodiment, slots 56 and 58 are formed by laser cutting. Because outer strap 52 and inner strap 54 must serve as substantial support for vane 20, relatively thick materials are required in the present invention;
Any of the cutting techniques described above can be used to create slots in such materials with satisfactory results.

Surface (not shown) outer strap 52 and inner strap 54 in proper coaxial relative position.
After being held firmly on top, the vane 20 is installed, for example, by sliding the vane 20 from the slot 56 of the outer strap 52 into the slot 58 of the inner strap 54. According to some embodiments of the invention, slots 56 and 58 are connected to respective bands 52 and 54.
penetrates through. However, it will be obvious to those skilled in the art that one of the slots 56 or 58 could be a blind hole, for example formed by electrical discharge machining, and the other could pass through the material of the strap. After installing the required number of blades 20 to form a 360 degree assembly,
Vanes 20 are welded to straps 52 and 54. During such welding, it is preferable to suppress heating of the inner band 54, outer band 52, and blades 20 as much as possible in order to minimize thermal distortion at this stage.

Referring now to FIG. 5, after the tack welding, structural welding is performed using, for example, gas tungsten arc welding and/or gas metal arc welding. The resulting welds 64 and 66 (not shown) structurally couple the vanes 20 to the inner and outer straps 54 and 52, although the straps still form a 360 degree annular structure. has been completed. Note that the welding procedure can be selected so that distortion caused by welding is minimized. For example, distortion can be eliminated or reduced by sequentially welding each pair of vanes on opposite sides of the assembly.
During this process, the inner strap 54 and the outer strap 5
By making 2 maintain a 360 degree annular structure,
The inherent geometric stiffness of the band can be used to distribute the forces caused by thermal distortion, thereby keeping the steam passage in the nozzle of adjacent vanes within design parameters. Become.

After ensuring that both ends of all the blades 20 are welded, the resulting assembly is subjected to stress relief treatment and tempering using normal protective atmosphere heat treatment techniques, so that the blades 20 remain in the assembly even after welding is completed. Possible residual stresses are removed and the areas affected by the welding heat are tempered. After the stress relief treatment, the inner strap 54 and the outer strap 52 are cut at two locations separated by 180 degrees along the cut plane between adjacent blades 20. For example, by using a curved cut plane as shown by dotted line 76 in FIG.
Can be divided into 180 degree fan-shaped parts. In addition,
Depending on the arrangement of the blades, a cut surface formed along a straight line or a combination of line segments may also be used. Preferably, the amount of material removed when making the cut along cutting plane 76 is minimized to minimize deviations from roundness when the ends are later engaged in the turbine. Cutting along cutting plane 76 may be performed, for example, using conventional moving wire electrode electrical discharge machining techniques, where, for example, 0.012 inches of material is removed. Compared to the radius of the partition plate, this amount of material removal is not a problem. Separately made 180 degree segments of outer ring 32 and inner ring 34 (FIG. 3) are then joined to the 180 degree sector. In that case, the smallest welded part 68
74, the outer strap 52 is fixed to the outer ring 32 and the inner strap 54 is fixed to the inner ring 3.
It is fixed at 4.

Turning now to FIG. 6, the mating surfaces of one assembled semicircular portion of the partition plate are shown. It will be appreciated that a flat radial mating surface 78 is provided on the outer ring 32 for contacting a corresponding mating surface of a mating member. Dowel holes 80 may also be provided for positioning and retaining a mating outer ring with dowel pins (not shown).

A flat radial mating surface 82 is provided on the inner ring 34 for contacting a corresponding mating surface of a mating member. As usual, mating surface 8
A tenon 84 can also be provided which projects from 2 and engages with a mortise (not shown) in the mating surface of the mating member. Also, a mating hole (not shown) on the mating surface of the other party.
A dowel pin 86 can also be provided which serves as a guide during assembly by being fitted into it. Note that the cut surface 76 is curved and at the same time the partition plate 2
It should be noted that while inclined to the plane of 6, mating surfaces 78 and 82 are preferably radial planes that extend to intersect the central axis. If the inner strap 54 and the outer strap 52 are cut along the plane of the mating surfaces 78 and 82, it is inevitable that the blade will be divided into two parts by the cut plane in the axial direction. Cut surface 76
By using this, all the blades 20 can be made perfect. Also, because mating surfaces 78 and 82 are flat, positioning and engagement of the two semicircular portions is facilitated.

Thus, in the partition plate according to the present invention, the 360-degree inner ferrule 54 and outer ferrule 52 are used to form a steam passage while utilizing their inherent geometric rigidity to distribute stress. In addition, by securing the strap to the ring with a minimum of welds, distortions due to stresses occurring during manufacturing are suppressed and reduced. Also, the use of curved cuts 76 intermediate adjacent blades 20 eliminates turbulence caused by blade segments with poor support strength. Since the inner band 54 and the outer band 52 form the structural support of the blade 20, when the inner band 54 and the outer band 52 are fixed to the inner ring 34 and the outer ring 32, the interface between the two is fixed. It is sufficient to perform the minimum amount of welding, and there is no need to consider whether the depth of penetration is large enough to reach the end of the blade.

Although a direct weld between the rings 32 and/or 34 and the vanes 20 is not required in the diaphragm according to the invention, this should not be considered to preclude overlapping welds. In some types of partition plates, the vanes 20 are located close to the upstream or downstream ends of the divider plate, so that even a minimal weld at the interface between the strap and the ring does not allow direct contact with the vanes. Sometimes it happens. The occurrence of such accidental contact should not be considered to exclude the partition from the scope of the present invention.

Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these specific embodiments. That is, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention as defined by the claims.

[Brief explanation of drawings]

FIG. 1 is an axial sectional view of a typical steam turbine, FIG. 2 is an enlarged sectional view of a portion of a steam turbine partition plate according to the prior art, and FIG. 3 is an enlarged sectional view of a steam turbine partition plate according to the present invention. FIG. 4 is a perspective view showing one step in assembling the steam passage of the partition plate, FIG. 5 is an enlarged view of the steam passage of FIG. 4, and FIG. 6 is based on the present invention. FIG. 7 is an enlarged view of the mating surface area of one semicircular portion of the assembled partition plate. In the explanatory diagram of main symbols, 20 is a blade, 26 is a partition plate, 32 is an outer ring, 34 is an inner ring, 52
are outer straps, 54 are inner straps, 56 and 58 are slots, 60 and 62 are vane ends, 64 and 66 are structural welds, 68, 70, 72 and 74
represents the smallest weld, 76 represents the cut surface, and 78 and 82 represent the mating surfaces.

Claims (1)

[Claims] 1. A method for manufacturing a partition plate for a turbine, comprising: forming two 360-degree bands of different diameters, and forming a plurality of slotted holes in each band for accommodating opposite ends of blades. forming the straps, placing the straps in concentric alignment with each other to define an inner strap and an outer strap, and welding the inner and outer ends of the vanes threaded through the inner strap and the outer strap, respectively; , cutting both the inner ferrule and the outer ferrule at two locations approximately 180° apart along first and second cutting planes located intermediate between adjacent vanes, with a generally flat surface at each end; forming a pair of 180° inner half-rings and outer half-rings having matching surfaces, and welding the inner half-rings and the outer half-rings to the inner strap and the outer strap, respectively; A method in which the cuts located midway between adjacent vanes do not lie in the same radial plane as the mating surfaces of the inner and outer half rings. 2. In the method according to claim 1, the step of cutting both the inner band and the outer band includes cutting a curved surface between adjacent blades to cut the first and second blades. How to create a semi-steam passage.